use-scroll-spy

Track scroll position and detect which heading is currently in the viewport, can be used for table of contents

Source

Docs

Package

Usage

use-scroll-spy hook tracks scroll position and returns index of the element that is currently in the viewport. It is useful for creating table of contents components (like in mantine.dev sidebar on the right side) and similar features.

Scroll to heading:

import { Text, UnstyledButton } from '@mantine/core';
import { useScrollSpy } from '@mantine/hooks';

function Demo() {
  const spy = useScrollSpy({
    selector: '#mdx :is(h1, h2, h3, h4, h5, h6)',
  });

  const headings = spy.data.map((heading, index) => (
    <li
      key={heading.id}
      style={{
        listStylePosition: 'inside',
        paddingInlineStart: heading.depth * 20,
        background: index === spy.active ? 'var(--mantine-color-blue-light)' : undefined,
      }}
    >
      <UnstyledButton onClick={() => heading.getNode().scrollIntoView()}>
        {heading.value}
      </UnstyledButton>
    </li>
  ));

  return (
    <div>
      <Text>Scroll to heading:</Text>
      <ul style={{ margin: 0, padding: 0 }}>{headings}</ul>
    </div>
  );
}

Hook options

use-scroll-spy accepts an object with options:

selector - selector to get headings, by default it is 'h1, h2, h3, h4, h5, h6'
getDepth - a function to retrieve depth of heading, by default depth is calculated based on tag name
getValue - a function to retrieve heading value, by default element.textContent is used

Example of using custom options to get headings with data-heading attribute:

Scroll to heading:

import { Text, UnstyledButton } from '@mantine/core';
import { useScrollSpy } from '@mantine/hooks';

function Demo() {
  const spy = useScrollSpy({
    selector: '#mdx [data-heading]',
    getDepth: (element) => Number(element.getAttribute('data-order')),
    getValue: (element) => element.getAttribute('data-heading') || '',
  });

  const headings = spy.data.map((heading, index) => (
    <li
      key={heading.id}
      style={{
        listStylePosition: 'inside',
        paddingInlineStart: heading.depth * 20,
        background: index === spy.active ? 'var(--mantine-color-blue-light)' : undefined,
      }}
    >
      <UnstyledButton onClick={() => heading.getNode().scrollIntoView()}>
        {heading.value}
      </UnstyledButton>
    </li>
  ));

  return (
    <div>
      <Text>Scroll to heading:</Text>
      <ul style={{ margin: 0, padding: 0 }}>{headings}</ul>
    </div>
  );
}

Reinitializing hook data

By default, use-scroll-spy does not track changes in the DOM. If you want to update headings data after the parent component has mounted, you can use reinitialize function:

import { useEffect } from 'react';
import { useScrollSpy } from '@mantine/hooks';

function Demo({ dependency }) {
  const { reinitialize } = useScrollSpy();

  useEffect(() => {
    reinitialize();
  }, [dependency]);

  return null;
}

Definition

All types used in the definition are exported from @mantine/hooks package.

interface UseScrollSpyHeadingData {
  /** Heading depth, 1-6 */
  depth: number;

  /** Heading text content value */
  value: string;

  /** Heading id */
  id: string;

  /** Function to get heading node */
  getNode: () => HTMLElement;
}

interface UseScrollSpyOptions {
  /** Selector to get headings, `'h1, h2, h3, h4, h5, h6'` by default */
  selector?: string;

  /** A function to retrieve depth of heading, by default depth is calculated based on tag name */
  getDepth?: (element: HTMLElement) => number;

  /** A function to retrieve heading value, by default `element.textContent` is used */
  getValue?: (element: HTMLElement) => string;
}

interface UseScrollSpyReturnType {
  /** Index of the active heading in the `data` array */
  active: number;

  /** Headings data. If not initialize, data is represented by an empty array. */
  data: UseScrollSpyHeadingData[];

  /** True if headings value have been retrieved from the DOM. */
  initialized: boolean;

  /** Function to update headings values after the parent component has mounted. */
  reinitialize: () => void;
}

function useScrollSpy({ selector, getDepth, getValue, }?: UseScrollSpyOptions): UseScrollSpyReturnType

use-scroll-into-view

use-viewport-size